Whey and Casein 101

January 14, 2023
| Created by Hannah Langley, MS, RDN, CD

Are you overwhelmed by the wide variety of protein powders in the sports nutrition aisle and aren’t sure which will best meet your individual needs? This article is part of a series, written by Harmons Dietitian Hannah Langley, to take an extensive look at protein powders and help you make the most informed choice when shopping for your health 

Milk contains two forms of protein, whey and casein. About 80% of the protein in milk comes from casein, while the remaining 20% is whey. Both whey and casein have high bioavailability and a complete amino acid profile, but their rate of utilization varies greatly. Whey has a high rate of utilization, while casein has a low rate of utilization 

Manufacturing – Concentrates vs Isolates vs Hydrolysates:

Many brands choose to separate the proteins into two different supplements due to the difference in rate of utilization. These milk proteins are separated from one another as byproducts of cheese production. Pasteurized milk is heated and treated with enzymes that cause casein to solidify into curds and separate from the liquid whey. The liquid whey and casein curds are then separated from one another and can be used to make dietary supplements (protein powder) or in casein’s case, cheese.  

The liquid whey undergoes microfiltration, where a combination of pressure and a semi-permeable barrier filters out the smaller molecules of lactose, carbohydrates, minerals, fat, and water. The protein molecules are too big to pass through the filter, resulting in a whey protein concentrate liquid. The product contains mostly whey protein, with small amounts of lactose, carbohydrates, minerals, and fat remaining.  

Whey protein isolate has a higher concentration of protein and minimal amounts of lactose, carbohydrates, and fat. To get whey protein isolate, the concentrated whey protein liquid undergoes additional filtration, known as ultrafiltration, to further remove remaining lactose, carbohydrates, minerals, and fat to isolate the whey protein.

Whey Protein Hydrolysate is sometimes referred to as ‘partially digested’ because it has undergone a process called hydrolysis. Hydrolysis is a process that naturally occurs in the digestive tract by enzymes to break down the chain of amino acids linked together as a protein. The protein is broken into smaller chains called peptides and into single amino acids, which can be readily absorbed by our body. To create whey protein hydrolysate, liquid whey is treated with a protein-digesting enzyme, heat, and an alkaline solution prior to being filtered and concentrated. The protein-digesting enzyme begins breaking the amino acid chains from proteins into peptides, the alkaline solution ensures the solution stays at a proper pH, and then the solution is heated to stop the enzyme from fully digesting the peptides. The resulting hydrolyzed liquid whey can then be filtered and concentrated.

The whey liquid, whether concentrated, isolated, or hydrolyzed, is loaded into a large dryer that blasts it with hot and cold air to dry the liquid whey into powder form and remove any remaining water. The dried and powdered protein product is then distributed to companies who can combine it with their own additional blend of flavors, ingredients, and additives to create the protein powders you see on our grocery shelves. 

As for casein, the curds are removed from the liquid whey and are washed with low-pH water to remove lactose, fat, and other molecules. The acidic environment also removes some minerals, and the curds are pulverized into a smooth paste. To bring the pH of the acidic casein curds to an optimal range, and to make the isolated casein proteins soluble in water, they are treated with an alkaline solution. This solution is typically sodium hydroxide or calcium hydroxide, to form sodium or calcium caseinate. 

Micellar casein is created by the microfiltration of skim milk. This process does not require the casein to be turned into curds and separated from the whey; casein micelles are large enough that smaller molecules of whey, lactose can be filtered away without having to solidify the curds.  

Some brands will include milk protein concentrate or milk protein isolate as a secondary ingredient in their protein powders. Milk protein is the natural combination of casein and whey, the two proteins are not separated as outlined above. Instead, the milk is filtered to concentrate both milk proteins. This type of protein retains more of the fat, carbohydrates, lactose, and minerals naturally occurring in milk.  

Best Use

Whey Protein Concentrate (WPC) has a protein content of up to 89% and contains small amounts of naturally occurring carbohydrates, fat, and lactose. Due to its high bioavailability and rate of utilization, WPC is best used for post-exercise recovery and increasing total daily protein intake.  

Whey Protein Isolate (WPI) has a protein content of 90% or greater with minimal carbohydrates, fat, and lactose. WPI likely has a slightly higher rate of utilization and cost than WPC due to the additional filtration it undergoes to further concentrate the protein and limit other substances. These factors make WPI best used for post-exercise recovery.  

Whey Protein Hydrolysate (WPH) has a protein content of 90-95%, and minimal carbohydrates, fat, and lactose. WPH has a high bioavailability and the highest rate of utilization of whey protein powders due to its highly absorbable peptide form. The additional processing required to hydrolyze the protein increases the overall cost of WPH. The best use of WPH is post-exercise recovery for high level athletes or individuals that are lactose intolerant and experience discomfort using WPC or WPI.   

Calcium or Sodium Caseinate are isolated casein proteins that are bound to either calcium or sodium to make them soluble in water. Sodium caseinate will contribute to daily sodium intake and would not be suitable for those with high blood pressure or hypertension. Calcium caseinate will increase daily calcium intake, which can be beneficial for those trying to increase total calcium or not suitable for those who may need to avoid it. They have a medium-high bioavailability and a slow rate of utilization, making their best use increasing total daily protein intake.  

Micellar Casein is the naturally occurring form of casein in milk products. It has a medium-high bioavailability and a slow rate of utilization, even slightly slower than caseinates. Its best use is for increasing total daily protein intake 

Key Takeaways

  • If using a protein powder to increase total daily protein intake, protein concentrates or casein are best. 
  • If using milk protein powder for post-exercise muscle recovery, whey protein isolate or hydrolysates are best. Protein hydrolysates are typically more beneficial for high-level athletes. 

Your Harmons Dietitian can help if you have questions, would like personalized product recommendations, or are curious about your individual protein needs. Reach out to dietitian@harmonsgrocery.com